In the field of cardiac pacemakers, there is a continuing need to provide an improved sensing system for accurately sensing and identifying patient heartbeat signals. As is well known, sensing of spontaneously occurring heartbeat signals is important for the proper operation of the pacemaker. Particularly for dual chamber pacing systems, it is important to be able to accurately identify sensed signals. For example, it is important to know when a signal that is sensed from the patient's atrium is of ventricular origin, i.e., a far field R-wave; or when a sense channel is missing a signal due to undersensing. Particularly in the case of a VDD single pass pacing system, the sensing from the atrial electrode or electrodes may be suspect, i.e., the source of the signal may be ambiguous.
It is known that unipolar sensing can provide certain sensing that bipolar sensing is unable to provide, and vice versa. What is needed is a pacemaker system providing selectable concurrent bipolar and unipolar sensing, and selectable switching for enabling the pacemaker to process the desired signal senses so as to optimize available information and provide for enhanced interpretation of the nature of sensed signals.